When you create a vdisk for swap, it does NOT use any storage. Really. The vdisk will acquire storage when Linux is short of storage and needs to swap. When a swap out is performed, CP obtains storage, allocates it to the Vdisk and then the swap operation occurs. Linux might see a 100MB virtual disk, but there is no cost in CP's real storage. Pretty cool stuff.
When Linux does not reference the data in the virtual disk for a while, it will be paged out, to expanded storage. This the optimal way of using expanded storage, and optimal for ensuring that when Linux is short of storage, it's performance does not suffer. Allocating expanded storage to a linux server as swap area is EXTREMELY expensive and takes an important resource and dedicates it to only one server. This platform is expensive, we make it cheaper by sharing resource effectively. Using vdisk and letting VM manage storage, expanded storage, and paging is the most efficient way of sharing resources. >From: James Melin <[EMAIL PROTECTED]> > >My understanding of Vdisk is that it is created using 'real' >memory that would otherwise be available for VM workload. Our >systems person does not want to let me use 'real' memory for a >vdisk swap area, and asked me if it was possible to use expanded >storage instead. I don't know, since I'm not the VM/z-OS guy. > >Opinion of the collected wisdom? > "If you can't measure it, I'm Just NOT interested!"(tm) /************************************************************/ Barton Robinson - CBW Internet: [EMAIL PROTECTED] Velocity Software, Inc Mailing Address: 196-D Castro Street P.O. Box 390640 Mountain View, CA 94041 Mountain View, CA 94039-0640 VM Performance Hotline: 650-964-8867 Fax: 650-964-9012 Web Page: WWW.VELOCITY-SOFTWARE.COM /************************************************************/ ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
